linux-ext4 - [PATCH v2 4/8] ext4: add the gdt block of meta_bg to system

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Date:   Mon, 19 Oct 2020 17:02:34 +0800
From:   Chunguang Xu <brookxu.cn@...il.com>
To:     tytso@....edu, adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org
Subject: [PATCH v2 4/8] ext4: add the gdt block of meta_bg to system_zone

In order to avoid poor search efficiency of system_zone, the
system only adds metadata of some sparse group to system_zone.
In the meta_bg scenario, the non-sparse group may contain gdt
blocks. Perhaps we should add these blocks to system_zone to
improve fault tolerance without significantly reducing system
performance.

Signed-off-by: Chunguang Xu <brookxu@...cent.com>
---
 fs/ext4/block_validity.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
index 8e6ca23..37025e3 100644
--- a/fs/ext4/block_validity.c
+++ b/fs/ext4/block_validity.c
@@ -218,6 +218,7 @@ int ext4_setup_system_zone(struct super_block *sb)
 	struct ext4_group_desc *gdp;
 	ext4_group_t i;
 	int flex_size = ext4_flex_bg_size(sbi);
+	int gd_blks;
 	int ret;
 
 	system_blks = kzalloc(sizeof(*system_blks), GFP_KERNEL);
@@ -226,13 +227,16 @@ int ext4_setup_system_zone(struct super_block *sb)
 
 	for (i=0; i < ngroups; i++) {
 		cond_resched();
-		if (ext4_bg_has_super(sb, i) &&
-		    ((i < 5) || ((i % flex_size) == 0))) {
-			ret = add_system_zone(system_blks,
-					ext4_group_first_block_no(sb, i),
-					ext4_bg_num_gdb(sb, i) + 1, 0);
-			if (ret)
-				goto err;
+		if ((i < 5) || ((i % flex_size) == 0)) {
+			gd_blks = ext4_bg_has_super(sb, i) +
+				ext4_bg_num_gdb(sb, i);
+			if (gd_blks) {
+				ret = add_system_zone(system_blks,
+						ext4_group_first_block_no(sb, i),
+						gd_blks, 0);
+				if (ret)
+					goto err;
+			}
 		}
 		gdp = ext4_get_group_desc(sb, i, NULL);
 		ret = add_system_zone(system_blks,
-- 
1.8.3.1